Dermatology Flashcards
what is the similarity and difference between macule and patches?
both are hyper pigmented flat lesions
a macule is <1cm
a patch is >1cm
what is the difference between a macule and a papule
macule is flat
papule is raised
what is the difference between a nodule and a papule
both are raised, well defined lesions
papules are <0.5cm
nodules are >0.5cm
what is the difference between a vesicle and a bulla
both are fluid filled lesions
vesicles are <0.5cm
Bulla are >0.5cm
what skin layer does a wound have to go down to to be classed as an ulcer
dermis
ulcer is a skin break that descends to the level of the dermis
what is the underlying cause of conditions that show purpura
low platelets (eg. von willebrand disease)
put the following topical steroids in order from least to most potent:
betnovate, hydrocortisone, dermovate, eumovate
- hydrocortisone
- eumovate
- betnovate
- dermovate
which condition can topical steroids cause a flare up of?
Psoriasis
what are the 3 functions of keratinocytes
produce keratin
absorb vit D
immune functions
name the 4 layers of the epidermis, from deepest to superficial?
basal layer
prickle cell layer
granular layer
keratin layer
on average, how long does it take a keratinocyte to travel from the basal cell layer to the keratin layer?
28 days
what are the non-nucleated remnants of keratinocytes found in the keratin layer called?
corneocytes
where do melanocytes migrate from? what is their role
the neural crest
produce melanin from tyrosine
what layer are langerhan cells found?
what is their primary function and their main distinguishing feature?
the prickle cell layer
main function: antigen presentation to T cells
distinguishing feature: Birkbeck granules
in terms of layers of the skin, what causes formation of bullae (pemphigoid)
diseases that cause alterations of the demo-epidermal junction
what is the primary function of the dermis?
to cushion and support the epidermis
what specific feature of the blood supply to the dermis allows for adequate thermoregulation?
the blood supply far outweighs metabolic demand
what is the difference in role between meissners corpuscles and pancinian corpuscles?
meissners corpuscles: found high in dermis, respond to light touch and vibration
pancinian corpuscles: found deeper in the dermis and respond to deep, heavy pressure
which cells are responsible for vit D production
keratinocytes
bullous pemphigoid is an autoimmune condition. Describe what the antibodies attack and what this results in
BP is a T2 hypersensitivity reaction
antibodies are produced against the hemi-desmosome proteins
hemi-desmosome proteins act as an anchor between the epidermis and basement membrane
BP results in interruption of the demo-epidermal junction and sub-epidermal blisters
what is the main differentiating factor between bullous pemphigoid and pemphigus?
whether there is mucosal involvement or not…
pemphigoid= no mucosal involvement (means the mouth is spared)
pemphigus= mucosal involvement
where do the blisters in bullous pemphigoid typically arise? how do they present
usually affect flexures of proximal limbs or trunk
large, tense, itchy blisters
what is nikolsky’s sign? is it positive or negative in bullous pemphigoid?
positive sign= when the top layers of the skin slip away from the lower layers when rubbed
nikolsky’s sign is negative in BP
how is bullous pemphigoid diagnosed?
what can be seen on immunofluorescence?
biopsy: sub epidermal blisters and inflammatory markers
immunofluorescence: linear IgG and complement (C3) along basement membrane
how is bullous pemphigoid managed?
local disease: high potency topical steroids
systemic: oral steroids +/- tetracyclines +/- anti-histamine
last resort: immunosupression
pemphigus vulgaris is an autoimmune condition. what protein are the antibodies produced against?
what is the function of this protein?
desmoglien 3
it is one of the desmosome proteins involved in cell-cell adhesions
compare the blisters seen in bullous pemphigoid and pemphigus vulgaris?
the blisters in pemphigus vulgaris are intra-epidermal
they are therefore much weaker and burst easier than bullous phemphigoid
describe the blisters seen in pemphigus vulgaris?
is the mucous membrane affected
multiple, painful, flaccid, fragile blisters
mucous membrane is affected- there are blisters in the mouth, conjunctiva, vulva
is nikolsky’s sign positive or negative in pemphigus vulgaris?
nikolsky’s sign +ive (blisters are intra-epidermal)
what can be seen on biopsy in pemphigus vulgaris?
acantholysis- separation of individual keratinocytes
which blistering condition causes “chicken wire deposition of IgG within the epidermis”
pemphigus vulgaris
how is pemphigus vulgaris treated?
local disease: topical steroids
systemic disease: oral steroids +/- immunosupression +/- rituximab
dermatitis herpetiformis is an AI skin condition. what antibody is produced?
what other disease process involves this antibody?
anti-TTG
coeliac disease
compare the site of blisters in pemphigoid vulgaris, bullous phemphigoid and dermatitis herpetiformis?
sub-epidermal: bullous pemphigoid and dermatitis herpetiformis
intra-epidermal: pemphigoid vulgaris
compare the locations of blisters in bullous pemphigoid and dermatitis herpetiformis (ie- flexor or extensor)
flexors: BP
extensors: dermatitis herpetiformis
describe characteristics of the itch in dermatitis herpetiformis
intensely itchy blisters
the itch can precede the blisters
how is dermatitis herpetiformis investigated? what do results show?
bloods: anti-TTG
biopsy: sub epidermal blisters with papillary microabscesses
immunofluorescence
what can be seen on immunofluorescence in dermatitis herpetiformis?
granular deposits of IgA within the papillae of epidermis
which blistering condition shows IgG and which shows IgA on immunofluorescence?
IgG = bullous pemphigoid
IgA= dermatitis herpetiformis
how is dermatitis herpetiformis managed?
1st line: gluten free diet +/- dapsone
what is a rare complication of dermatitis herpetiformis
increased risk of small bowel lymphoma
how many peaks in incidence is there in psoriasis?
2 peaks
1 in 20 y/o’s
1 in 50y/o’s
which drugs can cause psoriasis?
B Blockers, lithium, anti-malarial drugs, swift withdrawal of topical or systemic steroids
in psoriasis, what does the increased epidermal proliferation result in?
hyperkeratosis: thickening of the keratin cell layer
parakeratosis: retention of nuclei in corneocytes
why does psoriasis cause parakeratosis (retention of the nuclei in corneocytes)
the increased proliferation reduces the time cells are allowed for migration and differentiation
what happens to the layers of the epidermis in psoriasis
absence of the granular layer
thickening of the prickle cell layer
munro abscesses: neutrophil filled abscesses within the statum corneum
name the 2 main pathological processes in psoriasis?
- increased epidermal proliferation
2. dilation and proliferation of dermal blood vessels (causes accumulation of immune cells, esp T cells)
what clinical sign is seen in psoriasis due to the dilated blood vessels? what is this clinical sign?
Auspitz sign
when the plaque is scraped away, there is pinpoint bleeding due to dilated blood vessels
what is the most common type of psoriasis
chronic plaque
does plaque psoriasis affect extensors or flexors?
usually extensors
eczema is more likely to affect flexors
what is koebner phenomenon, seen in psoriasis?
when psoriatic plaques develop at site of trauma 2-6 weeks after trauma has occurred
when is guttate psoriasis seen? what age group does it tend to affect?
tends to follow an infection, especially strep throat
affects younger patients, 15-25 y/o’s
which type of psoriasis is pear-dropped in shape?
guttate psoriasis
how is guttate psoriasis managed?
self limiting- resolves in 6 weeks
which type of psoriasis can be precipitated by removal of potent steroids?
erythrodermic psoriasis
which type of psoriasis can result in complete failure of the skin?
erythrodermic psoriasis- the plaques fall off in large sheets
what is considered 1st line topical therapy in psoriasis to reduce the rate of cell devision?
vitamin D analogues - calcitriol
in which forms of psoriasis are steroids used?
palmo-plantar and flexural disease
which areas of the body does flexural psoriasis tend to affect?
develops in the groin, axilla or under the breasts
mostly in the elderly
what do NICE recommend as 1st line treatment in psoriasis?
potent corticosteroid alongside a vitamin D analogue for up to 4 weeks
what do NICE say is the 2nd line treatment for psoriasis management?
increase dose of vit D analogue
what is considered the longest duration of treatment with topical steroids in psoriasis? why is this?
do not use topical steroids for > 8 weeks
they cuse skin atrophy, striae and rebound symptoms
which type of psoriasis can photodynamic therapy be considered 1st line?
guttate psoriasis
how can guttate psoriasis be differentiated from pityriasis rosea?
presence of the herald patch indicates pityriasis rosea
herald patch is the lesion of the initial eruption
other then in guttate psoriasis, when else is photodynamic therapy indicated?
more widespread, severe disease
what is the mechanism of action of photodynamic therapy in psoriasis?
aims to damage the keratinocytes DNA to halt proliferation
mutations in what protein can contribute to atopic dermatitis?
mutations in fillagrin protein
it is responsible for maintaining the waterproof, protective nature of the keratin layer
how does the distribution of rashes in atopic dermatitis differ between infants and children and adults
infants: usually affects extensor surfaces
children and adults: usually affects flexor surfaces (wrist, cubital and popliteal fossa)
what is the diagnostic criteria for atopic dermatitis?
itch +3 of:
- visible flexural rash or history of one
- personal history of atopy
- dry skin in the past year
- onset before age 2
which condition presents with monomorphic punched out lesions and is considered an emergency?
what is the underlying causative of this?
eczema herpeticum
infection caused by herpes simplex 1
how is eczema herpeticum treated
IV aciclovir
in which patients is eczema herpeticum commonly seen?
young children with existing atopic eczema
when should emollients be used in atopic dermatitis?
always! emollients should be used even if the eczema is clear!
what is tacrolimus? when can it be used?
it is an immunosuppressant (a steroid sparing agent)
can be used in patients that require continual use of oral steroids